doc rule_set/_index.md: fix and move link
doc rule_set/_index.md: fix and move link

The end of the path for the Taxonomy link was wrong and assigned to an
unexpected word in the sentence. Address both issues.

Signed-off-by: Stephen Lawrence <4e793ced895c01a9ab00954a3eb58bff976c9ded@renesas.com>

GENIVI/vehicle_signal_specification,GENIVI/vehicle_signal_specification